Recent 7xxx aluminum alloys have been designed for the finite use of thick semiproduct
with contolled amount of constituent phases which mostly evolve during ingot preheat. In this
study, the effects of constitutional change and preheat conditions of 7175 and 7050 type alloys on the
evolution of constituent phases [M-, T-, S-phase and dispersoid] are presented. The constiuents
evolve depending on the constitutional effect, primarily the change of Zn:Mg ratio, preheat condition
comprising temperature and cooling rate following preheat. T- and M-phase are reprecipitated during
cooling after preheat, depending on the alloy constitutions. S-phase is evolved depending on the
constitution and preheat temperature, rather than preheat cooling rate. Prominent precipitation
temperature interval of constituents are discussed in view of quaternary phase evolutions. In addition,
evolutions of dispersoids together with M-phase are discussed. Specific alloy designs and preheat
conditions could provide controlled microstructures for the thick 7xxx semiproducts.